this is for county road the county road systems out there. we are looking into putting abs plastic (dual wall) pipe under our roads in places were corrigated steel pipe rust out in a matter of 10 years or less. wondering if any of you have tried this and what your thoughts are, i'm not to fond of doing this i guess for structural reasons but am willing to try it. our county is in southeast iowa were there is alot of farm field run off and freeze/thaw and heavy farm machinery on our roads. thanks
How much cover do you have over the pipe? 3 feet or better as long as you backfill with gravel you should be fine. Less then that I would take a look at concrete pipe. Just remember when looking at the cost of concrete pipe over plastic that with concrete you don't need stone.
Our county is doing it all over driveways and county roads for the last 5 or mare years. I have seen many roads with no more than 10-12 inches cover and no problems yet. They are useing recycled concrete or asphalt as backfill. Alot of our county roads see heavy dump truck traffic but not a lot of freeze thaw here.
The local townships are usung ads pipe and minimal cover. In some cases less than 1/2 the diameter of the pipe and they use alot of 15". Occasionally they have a problem, personaly I like to have my pipes deeper, usually the diameter of the pipe for a minimum or if I can I'll use old gas transmission pipe. .281 wall or thicker. There are several places where I can buy used gas pipe for very close to the cost of ads.
I build a lot of logging roads, and I really like the double wall (smooth bore) corrugated plastic pipe. I have no freeze-thaw, but I do have about every other kind of abuse possible. I sometimes have the loggers scraping the roads and taking almost all the cover off the pipe, dragging loaded trucks over them with skidders when the roads are saturated, and everything else you wouldn't want them to do. I find the most important thing to do is to be very conscientious about packing the soil under and around the sides of the pipe. The concrete pipe won't hold up to loaded log trucks either if it is poorly installed. The plastic pipe is actually tougher in my opinion than concrete, since rcp has no flex. It is certainly easier to handle. I put one in recently in pure sand, and since it was a fresh install w/ no rock or clay, the logger agreed to lay mats over it. The timber buyer called me and said they had finished logging but I needed to come replace my junk pipe. When I started digging it up, I realized when picking up the mats, loader operator had stabbed the grapple so deeply into the ground he had torn through the pipe in 2 places. The timber buyer stopped talking warranty and signed a new invoice. The grapple would have crushed a concrete pipe, too. I bid a job in the National Forest that involved replacing about 20 crossings made with corrugated steel that was rusting out. The bid specified concrete pipe so I called the district engineer and laid out my list of reasons the plastic pipe was better. She said she agreed with everything I said, and that I had laid out my case very well, however....They used controlled burns, and that pipe burnt like gasoline right through under the road. So, we used concrete.
I would be interested in your list of reasons why plastic is better. Do you use the type of pipe with the plastic bands at the joints or the type that interlocks and why one or the other is better. THANKS FOR ALL THE REPLYS
I build logging roads in the Pacific Northwest. All of the timber companies that I work for use CPP/ABS on all ditch relief crossings as well as stream crossings that require a 48" or smaller pipe. CMP, a CMP Multiplate or occasionally a bridge is installed when larger/wider crossing are required. Storm runnoff in this part of the country consist of a lot of organic acids that build up in the topsoil from natural regeneration of vegetation. These acids quickly remove the galvanized coating thereby allowing the pipe to rust and subsequently fail. Thirty five to forty five inches of rain a year of course greatly accelerates this failure. I am also told that gov't biologists have determined that a single spec of rust in a fish bearing stream will instantly kill any Salmon or Stealhead that comes in contact with said spec????????????????? In my experience the biggest problem with CMP these days is poor quality as I have dug up countless sections of 20+ year old CMP that has some rust inside but nowhere close to failure. To answer your questions: CPP/ABS withstands continuous heavy loads just fine even at depths as shallow as 12" of cover. Loaded log trucks here gross anywhere from 80 to 100 thousand pounds. A single pipe often will have 20 or more 80 thousand pound loads a day cross over it for weeks in mountainous terrain. Thats roughly 1.5 million pounds per day! CPP is somewhat flexible so it withstands a huge amount of deflection at shallow depths and still maintain its shape. Metal often gets ovaled and easily develops dents in the top from vehicle traffic with less than 24" of cover. Most of my crossings have shallow inlets with outlets often much deeper. In my case the flexibility of CPP greatly reduces installation costs as it doesn't require an absolutely perfect bed to lay in, slight bends and imperfections do not affect the performance or lifespan of the pipe as long as it drains. For flatter shallow installations such as driveway crossings I would recommend much more emphasis on grade of course. Ease of installation, one man, one machine can handle installation of 3 or 4 sections of 24" CPP without to much trouble. A two man crew can fly. Plastic bands are similer to metal bands except they come with manufacturer supplied zip ties instead of nuts and bolts. First time I saw the zip ties I wasn't impressed but I can honestly say I have yet to see a joint failure. Plastic bands reduce costs as they are really easy to install and do not require repeated hammering and tightening or air tools like the steel bands. Have extra zip ties on hand, occasionally they do break. Twistlocks, interlocks or any kind of rubber gasket jounts are a PIA. Sometimes required when continuous high flow is a concern. I believe these styles are primarily intended for municiple storm sewer applications. Interlock types of joints must be absolutely clean and require a lot more effort to properly install. CPP is easily cut with a chainsaw, no sparks! Biggest drawback with CPP in my experience is although flexible it is brittle so care must be taken when backfilling. Rocks up to about a foot or more are fine but don't dump anything larger from 10' high as it will go right through. Once you have the pipe covered your ok but as with any pipe installation care should be taken when backfilling. As mitch504 says CPP does burn like a barrel of diesel. Controlled burns and slashpile burning is common practice on public and private timberlands in the spring and fall here as well. Slashpiles are placed as far from CPP as possible and the folks that do the burning go to great lengths to avoid burning pipes out.
When we install our cmp we bed ours with 3/4" road stone 2 to 3 feet out and half way up the pipe then tamp it in place with a hand air tamper that has a 6inch thumper head on it, believe it or not if tamped to much it can lift the pipe up off the bottom of the grade, then start back filling with salvaged dirt rolling (compacting) it with a motorgrader. So how do you compact the the bedding material so not to lift the plastic pipe off the grade and from what i have heard it needs to be compacted all the way up and around the pipe before starting back filling?
The HDPE pipe has its place; ADS is brand name, HANCOR is another, but you are going to have to follow the manufacturers recommendations for installation and completely blind it with aggregate at the very least to the spring line and if it is larger than 24" to the top of pipe. I just finished replacing 100 feet of 54" that collapsed along the vertical axis because of no rock bedding and 20' feet of fill over the top of it. We replaced it with Class III RCP, thats the only way the ultimate owner would accept it. This was going behind another contractor and repairing previous damage. The HDPE had only been in the ground for 5 years. We are currently awaiting a change order to replace more that has collapsed. Don't take me wrong, I like the ease and speed of laying HDPE over RCP and have laid 1000's of feet of both. When backfilled according to the recommendations, HDPE will last a very long time. But I would add that; after you include the cost of rock, trucking and handling, I doubt that there will much difference in cost between the 2.